2852 - Impact of Body Composition on OAR Dose in Locally Advanced Cervical Cancer Treated with HDR Intracavitary-Interstitial Applicators
Presenter(s)
J. Tang1,2, C. Oska3, I. Small4, K. J. Mehta2, and R. Yaparpalvi5; 1Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, NY, 2Department of Radiation Oncology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, 3Montefiore Einstein Comprehensive Cancer Center, Bronx, NY, 4Albert Einstein College of Medicine, NYC, NY, 5Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY
Purpose/Objective(s): Higher body mass index (BMI) has been associated with lower late gastrointestinal (GI) toxicity in locally advanced cervical cancer when compared to underweight patients. In addition, patient characterized as obese reported less intestinal toxicities in EMBRACE 1. However, the brachytherapy dose contribution is not well studied in the setting of hybrid brachytherapy (BT) applicator. In this study, we hypothesized that higher BMI would decrease the small bowel (SB) dose delivered in HDR BT.
Materials/Methods: Patients with locally advanced cervical cancer that received definitive chemoradiation followed by BT boost from 2023-2025 were included. Baseline characteristics were collected including BMI at the time of brachytherapy boost. Body fat percentage (BFP) is calculated using (1.2*BMI) + (0.23*age) - 5.4 for female. BT dose of 0.1cc, 1cc, and 2cc were collected as % of prescription dose. The effects of BMI and BFP on dose were analyzed using linear mixed effects models yielding p-values and confidence intervals that account for the correlation between multiple observations from the same patient. Statistics performed with STATA v16.
Results: 56 patients with 221 BT plans were included. Baseline characteristics were as followed: median (IQR) age 54.5 (42-62.5), # of fraction 4 (3-4), # of needles used per fraction 2 (0-3). 87.5% patients received 7 Gy per fraction. Mean (std) BMI 29.5 (8.1), BFP 42.3 (10.0), HR-CTV 26 cc (14). The mean D0.1cc, D1cc, D2cc %Rx (SD) for rectal were 55.4% (18.6), 45% (15.4), 41.4% (13.9), for sigmoid were 63.9% (17.2), 52.5% (14.3), 47.8% (13.3), for bladder were 83.3% (13.6), 71.0% (11.2), 65.6% (10.6), and for SB 51.4% (22.9), 42.1% (19.6), 38.0% (17.5), respectively. Assessing BMI association with OAR dose, only SB dose was significant with coefficient of -1.14 (95% CI -1.83, -0.44, p=0.001), -0.91 (95% CI -1.51, -0.31, p=0.003), -0.84 (95% CI -1.37, -0.31, p=0.002) for D0.1cc, D1cc, D2cc respectively. Assessing BFP association with OAR dose, SB and rectal dose were significant with coefficient of -1.03 (95% CI -1.59, -0.47, p<0.001), -0.87 (95% CI -1.34, -0.39, p<0.001), -0.78 (95% CI -1.20, -0.36, p<0.001) and 0.52 (95% CI 0.06, 0.99, p=0.027), 0.49 (95% CI 0.11, 0.87, p=0.011), 0.47 (95% CI 0.12, 0.81, p=0.008) for SB and rectal D0.1cc, D1cc, D2cc respectively. Of SB dose, only D2cc was directly associated with HR-CTV with coefficient of 0.23 (95% CI 0.01, 0.45, p=0.037). However, HR-CTV size was not associated with BMI nor BFP.
Conclusion: Our study demonstrates a statistically significant inverse relationship between BMI and the dose received by the small bowel. This association is even stronger when we examine patients' body fat percentage in relation to small bowel dose, suggesting that visceral fat may help reduce the small bowel dose during brachytherapy. Our findings offer a dosimetric explanation for and enhance our understanding of the lower GI toxicity experienced by patients with higher BMI.